import {
    ADD_NUMBER,
    SUB_NUMBER,
    INCREMENT,
    DECREMENT
  } from './constants.js';

  const defaultState = {
    counter: 0
  }
  
  function reducer(state = defaultState, action) {
    switch (action.type) {
      case ADD_NUMBER:
        return { ...state, counter: state.counter + action.num };
      case SUB_NUMBER:
        return { ...state, counter: state.counter - action.num };
      case INCREMENT:
        return { ...state, counter: state.counter + 1 };
      case DECREMENT:
        return { ...state, counter: state.counter - 1 };
      default:
        return state;
    }
  }
  
  export default reducer;
  